Genomics 101: How can genomics help us understand rare conditions?

In this series, ‘Genomics 101’, we go back to basics and explore some of the most important topics in genomics. In this blog, we explain the vital role of genomics in helping us better understand and treat rare conditions.  

First things first, what is a rare condition? 

Broadly, a condition is considered as ‘rare’ if it affects a small number of people in the general population.  

The exact definition varies country to country, but in the UK a condition is rare if it affects less than1 in 2,000 people. 

There are currently estimated to be over 7,000 rare conditions, with new ones continually being identified as research advances.  

Most rare conditions have a genetic cause 

Around 80% of rare conditions are genetic. In other words, they are caused by one or more genetic change(s).  

A genetic change, also known as a genetic variant, is when a change has occurred in the sequence of someone’s DNA, sometimes affecting the way their body functions and develops.  

These changes can be inherited from one or both parents, or can even occur on their own at random.  

Studying all of someone’s DNA, which we call their genome, is a vital part of better understanding how and why rare conditions develop, as well as what we can do to treat them. 

Why is rare condition research important? 

Despite their name - rare conditions are collectively common, with 1 in 17 people in the UK being affected by them at some point in their lifetime.  

Though each individual condition may only affect a few people (or just one person in some cases), together they represent a major public health issue, with around 3.5 million people in the UK living with one. 

Many of those in the rare community experience a long and complicated journey for answers about their condition. This journey is sometimes referred to as the diagnostic odyssey. 

People can spend years going to appointments and having tests, without ever receiving a clear answer.  

This can happen for several reasons, such as: 

1) Symptoms for rare conditions can be similar to common conditions 

2) The same genetic condition can present very differently between individuals 

3) As each rare condition affects so few people, clinicians may not be familiar with them or know to test for them 

All of these delays and constant uncertainty can have a significant impact on quality of life. As well as persistent or worsening physical symptoms, people living with or caring for someone with a rare condition often face wider mental, emotional and financial challenges. 

Rare condition research is essential to help close this diagnostic gap. 

How can genomics help? 

As mentioned above, most rare conditions have a genetic cause.  

Analysing all of a person’s DNA, known as genomic testing, can therefore be a powerful tool for diagnosis.  

An example of where genomic testing has progressed our understanding of rare conditions is the 100,000 Genomes Project.  

This study, delivered by Genomics England in partnership with the NHS, sequenced the genomes over 85,000 individuals affected by rare conditions and cancer.  

The project demonstrated how genomic testing can make a real difference for those living with rare conditions and their families, with a new diagnosis being returned for 25% of participants. 

14% of these diagnoses were a result of searching in regions of the genome that would have been missed by other testing methods.   

Advances in the space: gene therapies and individualised medicine 

As it stands, only around 5% of rare conditions have an approved treatment. There is therefore a key need to advance our understanding, so that effective treatments can be developed.  

Understanding more about the genetic causes behind rare conditions can be an important first step in developing targeted treatments. Advanced technologies have transformed our ability to do this, for example:  

Gene panels (testing a set of genes linked to a symptom or disease group) 

Whole genome sequencing (reading almost all of the genome) 

In addition, for some rare conditions where the genetic cause is known, precision or individualised treatments may be possible. These therapies are designed to target the underlying genetic change(s) responsible for the condition.  

Examples include gene therapies and RNA-based medicines such as antisense oligonucleotides.  

As our understanding of the human genome continues to grow (driven by advances in genomic technologies) so too does the potential to develop more personalised approaches for people living with rare conditions. 

Looking ahead 

Even with modern genomic tests and technological advances, a large proportion of people with rare conditions remain undiagnosed, and there is still lots of work to be done. 

In 2023, Genomics England announced a new programme in collaboration with the Government known as the ‘Rare Therapies Launch Pad’. 

The programme aims to develop a pathway for children with rare conditions to access therapies made specifically for them. 

If you want to learn more about progress in rare conditions, check out our blog for Rare Disease Day 2026.